The present invention relates to a catalytic heater apparatus for gaseous fuel, including a combustion cell having a rear wall traversed by a supply conduit for fuel gas, and into which a front wall formed by a porous refractory substrate impregnated with an oxidation catalyst is fitted, with a reflector extending in front of this front wall, and an annular nozzle connected to a supply source of air surrounding its periphery.
The advantage of this type of apparatus over heaters that operate solely by radiation is that there is less stratification of the layers of air because of the forced mixing of the products of combustion with the ambient air. This mixing is made possible by the fact that the catalytic combustion temperature is on the order of 600.degree. C. and is thus below the threshold beyond which carbon monoxide and NO.sub.x are produced, so that the combustion gases need not be evacuated as long as they do not contain toxic products. Nevertheless, the combination of convection heating with this type of catalytic burner requires the use of a valve and fresh air channels and distribution nozzles, to mix the fresh air with the hot combustion gases. The resultant apparatus is much more complicated in structure and thus more expensive to make.
The object of the present invention is specifically to make it possible to reduce the costs for machining the components of the apparatus and the costs for installing it.
To this end, the subject of the present invention is a catalytic heating apparatus for gaseous fuel including a combustion cell having a rear wall and a front wall connected together along respective peripheral edges and a supply conduit for fuel gas connected to the combustion cell through the rear wall. The front wall is a porous refractory substrate impregnated with an oxidation catalyst. A nozzle is defined adjacent to the peripheral edge of the porous refractory substrate and has two parallel lips extending in surrounding relation to and in front of the porous refractory substrate. The nozzle defines a substantially continuous opening directed toward a central axis of the combustion cell. A peripheral reflector projects in front of the porous refractory substrate from one of the lips. The peripheral reflector and the connected lip are provided by a same profile section element, with spacing braces positioning the profile section element around the cell. A seat is defined by a rear free edge of the profile section element and a partition member is provided which has a peripheral edge lying on the seat. A clamp engages the adjacent edges of the partition and the seat. A central opening is defined through the partition and a fan is fastened thereto. A channel is defined between the partition and the rear wall of the combustion cell to supply the nozzle with pressurized air from the fan.
The number of parts to be assembled have been reduced to a minimum, as has the number of fasteners. Moreover, the largest possible number of parts can be made from a profile section and, accordingly, require a minimum of machining operations. Consequently, the catalytic heating apparatus that is the subject of the invention can be made at a very competitive price, despite the elevated cost for the catalytic combustion cell, the porous refractory substrate of which is impregnated with platinum.